Most ambient-temperature batteries and many capacitors and fuel cells incorporate various forms of carbon such as carbon black, graphite, and activated carbon. In the context of this application, carbon refers to a solid carbonaceous material having at least 50% carbon with a relatively small proportion of hydrogen. In addition, oxygen may be present in the carbon as well as ash in an amount representative of the feedstock from which the carbon was formed. The stable and conductive material properties of carbon allow carbon to be used as an electrode matrix into which other materials may be incorporated. In some instances, the carbon or active sites in the carbon may participate in key electrochemical reactions. In other instances, a catalyst may be supported on the carbon.
In many existing batteries, carbon is dispersed throughout the electrode but not fully connective. Carbon may be added to the electrodes of these batteries as a few percent in a mixture that is stamped into the shape of the electrode. One problem with this electrode composition is that as other materials enter or exit the electrode during the operation of the battery, possibly expanding or shrinking the electrode in the process, the structural integrity of the matrix may be lost. Shedding may occur as in the case of existing lead-acid batteries. Further, the shape of the electrode may eventually become distorted and adversely affect battery performance, for example when recharging metallic lithium primary batteries. In addition, when electroplating highly reactive metals such as lithium onto electrode materials that include chemical moieties such as oxygen, these moieties may adversely interfere with the electroplating process.
Furthermore, a standard approach to battery design is to minimize the distance between electrodes to a distance typically ranging from about 0.03 to about 10 mm so that diffusion may provide the primary mechanism of ion transport between counter-electrodes. For larger-scaled power sources such as those used in plug-in hybrid electric vehicles or grid electricity storage, other mechanisms of ion transport such as convective flow may enhance the diffusive transport of ions.
A need exists in the art for a carbon electrode that retains its shape as an electrically connective matrix of carbon in the absence of all other electrode materials except the carbon.